Pipeline 2 fails because the $divide operator only supports numeric types
Fails – can be interpreted in several ways
a) Fails: you will not get a result document output
b) Fails: you will not get a result document with a correct value (failed)
c) The pipeline as such before running has a failure as it is not consistent to the specs
What kind of failure(s) do you mean here?
The meaning of “fail” here is fairly straightforward. If you attempt to run the indicated $aggregation pipeline, you will get an error. Try it.
Hi David
I tried it on my system with Mongo v4.0.5. It run well. Meaning I have received a document with no error announced but the result return value in the document was a null.
I expected that it will not run through and give an error.
No, it doesn’t. Remember a couple of setup issues. First of all, you need to create the indicated collection. Here’s how I did it from the shell
use m121
db.testcollection.insertOne( { "a": [1, 34, 13] } )
now check that you have set it up correctly:
db.testcollection.find()
should return something like
{ "_id" : ObjectId("5c50a1bd2f93d04ec2da131b"), "a" : [ 1, 34, 13 ] }
Now run the indicated $aggregation pipeline
db.testcollection.aggregate([
{"$project": { "a_divided" : {"$divide": ["$a", 1]} }}
])
This fails on all versions of MongoDB that I have (3.2 – 4.0). Try it again. I think you’ve made a mistake in your setup.